The present invention relates to a bumper for a vehicle having an extruded light metal alloy hollow section comprising section walls in the form of a compressive strut and a tensile strut which are spaced apart and a pair of transverse walls joining them.
Such a bumper is described in CH 689 638 A5. In that bumper at least one transverse strut is provided between the transverse walls and joins the two section walls to each other such that the hollow section is subdivided into chambers. Further, a vertical strut is provided between the section walls joining the two transverse walls to each other, and defines a primary deformation part with chambers bordering on the compressive strut and a secondary deformation part with chambers bordering on the tensile strut of the hollow section. This design should provide a high degree of stability in shape along with adequate capacity for compensation of deformation energy on impact.
With the knowledge of this sate of the art the object of the present invention is to provide an improvement in the strength ratios also when transverse walls of the kind described are not present or only to a small extent. In addition the strength of such a hollow section should also be improved if holes are provided in one or the other transverse or section wallsxe2x80x94for example for attaching screws or similar connecting elements.
In accordance with the invention a reinforcing bead is provided in the interior of the section on at least one of the transverse walls and/or on a section wall joined to it. According to another feature of the invention, the reinforcing bead is situated in the corner region between the transverse walls and at least one of the section walls connected to them, this preferably in the adjacent corner regions between the transverse walls and the inner section wall facing the vehicle.
As a result, deformation forces experienced on impact or the like are taken up and re-directed in the direction transverse to the section walls. Due to such a jump in stress, the strength of the bumper is greatly increased.
The above mentioned jump in stress may also be reinforced by providing in the outer face of the reinforcing bead a longitudinal groove which runs parallel to the neighbouring section wall and is delimited a distance from it by a longitudinal rib which is part of the reinforcing bead.
It has been found favorable for the recesses or longitudinal grooves or the longitudinal ribs of facing reinforcing beads, which are aligned with each other on a section wall, to lie as in a common plane. Further, in accordance with the invention, the longitudinal ribs should be shaped such that it defines an outer face of the reinforcing bead which runs approximately parallel to the section wall which also delimits the longitudinal groove, i.e. forms a part of this. Furthermore, the breadth of the longitudinal groove should preferably correspond approximately to the breadth of the longitudinal rib and the depth of the longitudinal groove should be about the same as its own breadth. In addition, it is also foreseen for the magnitude of the depth of the longitudinal groove to be one third to one half of the height of the reinforcing bead. The thickness of the section wall should thereby correspond at least to the breadth of the neighbouring longitudinal groove.
The result is a hollow section the resistance of which to deformation forces under collision conditions or the like is greater than that of comparable sections without the corner designed according to the invention.